In the manufacture of semiconductors, the contamination of wafers by particles generated in the manufacturing process is known to severely decrease the yield of viable integrated circuit chips. Accordingly, at all stages in the semiconductor manufacturing process, care is taken to avoid contamination of wafers, such as by use of clean rooms and by use of equipment which does not produce particles while treating wafers.
Previously, convection ovens have been used which employed an inert gas to transfer heat to the wafers. An example of such an oven is found in U.S. Pat. No. 4,597,736 to W. Moffat. In this patent, a preheated inert gas is injected into an oven wherein wafers are heated due to convective heat transfer from the inert gas.
Even though the inert gas is very pure, it is possible for the gas to pick up particles somewhere before release in the oven. Also, particles which are already on the wafer, may be dislodged by gas flow and redistributed from one location to another.
An object of the invention is to improve convective ovens for heat treatment of semiconductor wafers and in particular to provide an oven having anti-contamination features protecting oven contents against foreign particulate matter.